Icebergs are edges of glaciers that have broken off and slipped into the ocean. Glaciers form on land by snow building up over thousands of years. Each layer of snow compresses those below until, 60 to 70 metres down, glacial ice forms. Glaciers then "flow" or "creep" towards the ocean under their own weight, and eventually slip in. The glaciers of western Greenland flow at speeds of up to seven kilometres a year, among the fastest moving in the world. After slipping into the ocean, the bergs float in frosty arctic bays melting slowly, if at all, until passing through the Davis Strait and into the Labrador Current which carries them south into Iceberg Alley. Once they head south, they rarely last more than one year.

Every year about 40,000 medium- to large-sized icebergs break off, or calve, from Greenland glaciers. Only about 400-800 make it as far south as St. John's, but these numbers can vary greatly from year to year. The chances of seeing icebergs in a particular area depend on the number of bergs, wind direction, oceans current and temperatures, and the amount of sea ice, or pack ice. Sea ice protects icebergs from the battering of waves and helps them last longer. Years of little sea ice cover are often years of few icebergs along Newfoundland's coast. Also, there may be areas where you can't see any, but 100 kilometres up the coast there might be dozens, so be prepared to travel around. And remember that icebergs are constantly on the move.

As glaciers creep over land, meltwater fills the crevasses and later freezes, creating clear, bubble-free ice. This shows up as bluish streaks in icebergs because of the light scattering characteristics of pure ice. Sometimes airborne dust from volcanic eruptions, or the wind, falls on a glacier and becomes trapped inside, forming a noticeably darkened brown or black layer. But because most volcanoes are south of glaciers and winds from the south rarely mix with Arctic air masses, there are very few pollutants in the ice.

Icebergs don't have a consistent speed. The size and shape of an iceberg, ocean currents, waves, and wind all affect its speed, and because of these forces often travels an irregular path that's two or three times the straight line distance it drifts south over a week or so. The average drift speed is around 0.7 km/h, although speeds greater than 3.6 km/h have been recorded.

Almost 90% of an iceberg is under water, hence the phrase "tip of the iceberg." Its maximum width under water is 20% to 30% larger than you can see at the surface. The average depth, or draught of an iceberg, is slightly less than its apparent length above water.

Icebergs can vary greatly in size, ranging from very large - greater than 10 million tonnes and hundreds of metres long - to large, medium, and small bergs. The smallest are termed "bergy bits," which are the size of a small house, and "growlers," which are the size of a grand piano. These smaller pieces are hazardous to ships because radar may not pick them up as they bob up and down among the waves. The average weight for a Grand Banks-area iceberg is 100,000-200,000 tonnes - about the size of a cubic 15-storey building.

In the Northern Hemisphere, the largest iceberg on record was encountered in 1882 near Baffin Island. It was 13 km long, 6 km wide, and was about 20 m above water. It weighed over 9 billion tonnes - enough for everyone in the world to drink a litre of water a day for more than 4 years. Icebergs from Antarctica can be many times larger. In 1987 an iceberg, with an area of 6,350 sq. km, calved from the Ross Ice Shelf. It weighed about 1.4 trillion tonnes and could have provided everyone in the world with 240 tonnes of pure drinking water.

Icebergs are often very unstable. The random shape combined with the varying degrees of melting and breakup means they can tip or roll suddenly. Generally, the most stable icebergs are tabular, while domed- and wedge-shaped bergs may roll completely over in seconds without any apparent reason.

It's about 10% as strong as concrete. This may not seem very hard, but it's a lot harder than ice your make in your freezer. A ship colliding with an iceberg almost certainly means disaster due to the enormous momentum involved and potentially massive contact region. The ice can literally generate hundreds of tonnes of force on a ship's hull, causing it to buckle, dent, crumple, and even tear apart.

Yes, icebergs often "ground" or reach the seabed and get stuck. This happens when fluctuating tidal currents or strong winds bring icebergs close to shore or onto shallow areas like reefs. At times, icebergs "scour" the ocean floor, creating irregular troughs that can be several kilometres long and up to half a metre deep. The Grand Banks are criss-crossed with iceberg scour marks, both recent and decades old.

Iceberg Viewing Tips

So you want to see an iceberg? Where do you go? When are icebergs around anyway?

Aside from an iceberg's shape and size, look for colour streaks, caves and tunnels, waterline notches, and even large rocks embedded in the ice. A few years ago the carcass of an unknown animal was spotted in a berg. You'll often see birds perched atop icebergs, and if they suddenly fly off, it might be a sign the iceberg is about to roll or break apart, a spectacular treat for the eyes and ears.

An iceberg can break apart or roll at any time, so it is extremely dangerous to approach one. The breaking or rolling creates a huge disturbance in the water, which can easily upset a boat, especially a smaller one, and when an iceberg splits apart it fills the nearby sea with literally millions of small pieces of hard ice that can surround or even hole a small boat. There is no "rule of thumb" for a safe distance as icebergs have varying shapes, and may have long underwater rams which pose a threat to all vessels. Generally, you should keep a minimum distance equal to the length of the berg between you and this massive piece of unstable ice, though safety can never be guaranteed. Any attempt to climb onto an iceberg is foolhardy in the extreme. Due to their instability, falling ice or a rolling berg could throw you into the frigid water before collapsing on top of you.

Icebergs are best viewed in late May and early June along the coast of Newfoundland, and between March and July along the coast of Labrador. Bergs are actually most plentiful in April and May but are often trapped in sea ice that prevents tour boats from operating. Usually, the last bergs melt away near St. Anthony in the first week of August, a few weeks earlier around Twillingate and St. John's. It's always a good idea to check with the Canadian Ice Service, local boat tour operators or Visitor Information Centres for current information.

In some years and in a few areas of Newfoundland's northeast coast, northward migrating whales and seabirds cross paths with southward drifting bergs. The number of bergs, water temperatures, the timing of bergs and migrations, and other natural factors have an effect. While the triple treat of this spectacle is not entirely uncommon, it should not necessarily be expected, even when travelling at the right time of year. Variations from year to year make it impossible to accurately forecast this most rare of natural wonders.

On average, icebergs are more plentiful as one travels further north up the east coast of Newfoundland and Labrador. Some of the more popular places from which to view icebergs from shore, or from tour boats, are from north to south: Cartwright, Battle Harbour, Point Amour, St. Anthony, La Scie, Twillingate, Bonavista, St. John's/Cape Spear and Bay Bulls/Witless Bay. All of these are accessible by road. The first three are on the coast of Southern Labrador and can be reached by car ferry between St. Barbe and Blanc Sablon. Check with local tour operators, Visitor Information Centres (internal link) and accommodations for iceberg conditions and tour information.

Viewing an iceberg from shore is affected by many variables: the elevation of viewpoint, the height of the berg, the clarity of atmosphere, and air/water temperature conditions. The chart below tells you what to expect from various distances:

Distance of Iceberg

Viewing Experience

Less than 5 km

Highly likely you will enjoy a wonderful view of this iceberg. Even better if the iceberg can be viewed from a hilltop.

Between 5 km and 10 km

A good view from a distance. If you have a camera with a good zoom lens you could get a nice photo. A set of binoculars will also give you a nice view.

Between 10 km and 15 km

Be sure to bring those binoculars or a good camera lens…or even a telescope. If you are determined to see a berg, it is still worth a try.